Megger MIT415, User Manual

Page: 7 / 14

DAR is the ratio between the insulation resistance values at
30seconds (assigned t1) and at 60 second interval (assigned t2). i.e.
after 30seconds and 60seconds.
DAR = 60 second value/30 second value
During all insulation tests the symbol
G
will flash indicating that a
test voltage is present.
(a) Insulation resistance testing-timed procedure.
1. Connect the test probes to the isolated circuit under test.
2. Turn the instrument ‘ON‘ by rotating the selector switch to the
required test voltage position.
3. Select the timed test (t) by pressing ‘PI/DAR/t’ function button
repetitively until the desired function is displayed.
4. Once selected, press and hold the [TEST] button to start the test.
5. To abort the test early, press TEST or LOCK [ ] buttons.
6. At the end of the tests, the voltage will be discharged.
(b) Insulation resistance testing – PI and DAR
The PI test will run for a period of 10minutes. After one minute a
test result is stored (t1). After 10 minutes a second test result is
stored (t2). The resultant ratio is then displayed on the screen.
The same procedure applies for the DAR timed tests, however the
test duration is 60 seconds, with the first result (t1) taken at 30
seconds and the second at 60 seconds (t2).
Results can be recalled to screen using the uA/v/s [
t
] keys.
Note: DO NOT press PI/DAR/t [
s
] as it will change the test mode
and erase the current results.
Continuity testing [
Ω
] and buzzer [ ]
1. Turn the instrument ‘ON’ by rotating the selector switch to
the desired
Ω
position.
2. If required the test lead resistance can be set to Zero (null) by
shorting the test leads together and pressing TEST. The null
[
z
] symbol will show when this has been achieved and the
display will read 0.00
Ω
.
3. Press the [ ] button to enable/disable the audible buzzer
function. When enabled, the sounder symbol will be shown on
the screen display. The pass threshold is set to 2
Ω
by default,
but is adjustable, as defined in Setup.
Note that the buzzer defaults to OFF on power-up.
4. Connect the test leads to the isolated conductor(s) under test.